1. Field of the Invention
The present invention relates to an imaging device for soft x-rays.
2. Description of the Prior Art
There are many types of previously known imaging devices for use with x-rays. For example, imaging devices for hard x-rays, i.e. x-rays having an energy in excess of 30 KeV, are typically used in the medical industry. Such hard x-ray imagers are advantageous since hard x-rays pass essentially without attenuation through air and thus are convenient for medical applications. Hard x-ray imagers, however, only enjoy a resolution of about one-fifth millimeter which, while adequate for most medical applications, is inadequate for many industrial inspection applications.
The previously known imaging devices for hard x-rays, however, have not proven satisfactory as imaging devices for soft x-rays, i.e. x-rays having an energy of less than 20 KeV, for a number of reasons. First, soft x-rays rapidly attenuate in air and thus are difficult for many applications, such as medical applications, where the x-ray radiation must necessarily pass through air.
A still further disadvantage of the imaging devices for hard x-rays is that many of the imaging devices utilize a beryllium window in the imaging device. Soft x-rays, however, are readily absorbed by the beryllium window used with these prior hard x-ray imaging devices so that considerable attenuation and loss of resolution results.
There are previously known soft x-ray imaging devices and many of these previously known devices use microchannel plates for converting and multiplying x-rays to electrons. In one such imaging device the microchannel plate was supported by spaced pins and the entire x-ray imager was employed in essentially a complete vacuum. Such a mounting system for the micro channel plate is disadvantageous since the microchannel plate may distort and warp the image. Furthermore, these devices must be used in a vacuum and therefore are inappropriate for most industrial applications.
In still another type of x-ray imaging device, the microchannel plate is supported in a housing by thin disks and the housing, in turn, is sealed. These imagers, however, are easily broken and/or become misaligned when subjected to shock. Similarly, the thin disks which mount the microchannel plate to the housing fatigue and sag over time which distorts the image. Furthermore, the atmosphere within the chamber becomes cloudy over time due to outgasing from the parts inside the chamber, and diffusion through the housing which adversely affects the image.